Another design to accomplish this same goal seems to be called the "safety shoe" [1]. I believe this is a horizontal bar placed under the open door which moves the airbridge down if it gets too close.
The idea seems to be that if the door touches the top of the sensor, it automatically lowers the jetbridge a few inches to prevent the door from being damaged. And I guess this can happen if the plane is being loaded improperly causing it to shift.
[1] PDF, 4MB: https://www.acesincusa.com/wp-content/uploads/2020/07/Safety...
I have also noticed in some jet bridges, you will see some kind of air sensor probe on the end of a coiled cord, which is very odd to me that this would inform the operation of the bridge. I can't find a photo of it readily, but it is definitely something I have noticed and puzzled about.